This invention relates to a process for producing decorative sheets to be used for various construction materials, furnitures, etc. The decorative sheet has a top coating layer having sharp concavities formed on the surface thereof by utilizing the liquid repellent performance possessed by the printed pattern layer contains a curable resin as the vehicle. The present invention also provides a process for producing decorative sheets having sharp concavities on the top coating layer at the portion corresponding to the printed pattern layer, and while also having excellent performances of solvent resistance, water resistance, abrasion resistance, weathering resistance and heat resistance, and further having excellent properties for smoothness of the surface of the decorative plate. The present invention further relates to a process for producing decorative plates using the above-described above decorative sheets.
A decorative plate having an unevenness effect corresponding to the printed pattern layer attached on a paper for a decorative sheet revealed thereon has been frequently used as a decorative plate since it can exhibit excellent design characteristics due to the corresponding embossed effect.
The method for obtaining a decorative plate having the above corresponding embossed effect may include:
1) the method in which a decorative sheet having a printed pattern layer is applied with embossing with a pattern pressing plate or a pattern pressing roll corresponding to the above printed pattern layer, and then the decorative sheet is laminated on a substrate for the decorative plate; PA1 2) the method in which a decorative sheet having a corresponding embossing is obtained by a combination of a printed pattern layer with a printing ink having the action of inhibiting curing of the curable resin during formation of the top coating layer and a curable resin for formation of the top coating layer, and then the decorative sheet is laminated on a substrate for the decorative plate; PA1 3) the method in which a decorative sheet having a corresponding embossing obtained by a combination of a printed pattern layer with a printing ink having the action of promoting curing of the curable resin during formation of the top coating layer and a curable resin for formation of the top coating layer, and then the decorative sheet is laminated on a substrate for the decorative plate; PA1 4) the method in which a decorative sheet having a corresponding embossing is obtained by a combination of a printed pattern layer having good permeability to the resin liquid to be used during formation of the top coating layer and a resin liquid for formation of the top coating layer, and then the decorative sheet is laminated on a substrate for the decorative plate; PA1 5) the method in which a decorative sheet having a corresponding embossing is obtained by a combination of a printed pattern layer having the action of inhibiting permeability to the resin liquid to be used during formation of the top coating layer and a resin liquid for formation of the top coating layer, and then the decorative sheet is laminated on a substrate for the decorative plate; PA1 6) the method in which a coating agent for formation of a top coating layer is coated and solidified on a base paper for a decorative sheet having a printed pattern layer, and then printing is effected on the top coating layer obtained with a printing ink containing a large amount of an extender pigment at a predetermined portion, thereby forming the decorative sheet with the printed portion on the top coating layer being made a convex portion by the above extender pigment, and the decorative sheet is laminated on a substrate for the decorative plate; PA1 7) the method in which a printed pattern layer having a liquid repellent performance is formed on a base paper for a decorative sheet, and then on the printed surface is coated and solidified a coating agent for formation of top coating layer, thereby forming a coating layer with the portion corresponding to said printed pattern layer being made concave through the liquid repellent performance possessed by the above printed pattern layer, and the decorative sheet obtained is laminated on a substrate for the decorative plate. PA1 Alcohol type: methanol, ethanol, propanol, butanol, ethylene glycol, methyl cellosolve, butyl cellosolve, methyl carbitol, benzyl alcohol, phenyl cellosolve, furfuryl alcohol, cyclohexanol; PA1 Active methylene type: dimethyl malonate, diethyl malonate, ethyl acetoacetate; PA1 Mercaptan type: butyl mercaptan, thiopheol, tert-dodecyl mercaptan; PA1 Acid amide type: acetanilide, acetanisidide, acetic acid amide, benzamide; PA1 Imide type: succinimide, maleinimide; PA1 Amine type: diphenylamine, phenylnaphthylamine, aniline, carbazole; PA1 Imidazole type: imidazole, 2-ethylimidazole; PA1 Urea type: urea, thiourea, ethyleneurea; PA1 Carbamic acid salt type: phenyl N-phenylcarbamate, 2-oxazolidone; PA1 Imine type: ethyleneimine; PA1 Oxime type: formaldoxime, acetaldoxime, methyl ethyl ketooxime, cyclohexanone oxime; PA1 Sulfite type: sodium bisulfite, potassium bisulfite.
Whereas, of the prepartion methods of the decorative plate having the effect of corresponding embossed effect of the prior art as described above, the method for preparing the decorative plate described in the above 1) can add an embossing corresponding to the printed pattern layer only with difficulty.
On the other hand, the methods for preparing the decorative plates described in the above 2) to 5) have drawbacks such that the depth of embossing is unstable, and yet that the scope of choice of the resin for a vehicle in the printing ink for formation of the printed pattern layer and the resin for formation of top coating is narrow, etc.
Furthermore, in the method utilizing a printing ink containing a large amount of an extender pigment of 6), the embossing effect is substantially visual, whereby not only is steric depth lacking, but also there is the limitation that the decorative plate obtained has a portion with a dense coloration degree formed necessarily at the convex portions, and yet a printed pattern with a printing ink containing a large amount of an extender pigment is formed on the outermost surface in the decorative plate. Therefore, drawbacks are involved in the surface characteristics of the decorative sheet. Furthermore, in the case where the vehicle in the printing ink used during formation of the printed pattern layer exhibiting the above liquid repellent action is a curable resin, since the curing reaction proceeds during the printing step, the viscosity of the printing ink changes depending on the degree of the curing reaction, whereby the amount of the printing ink attached in the printed pattern layer or the attachment strength becomes varied.
Consequently, the liquid repellent performance of the printed pattern layer obtained will become unstable, thus having the drawback that the unevenness effect in the decorative sheet will become nonuniform. On the other hand, in the case where the vehicle in the above printing ink is a curable resin, and also an acid catalyst, etc. for promoting curing of the above resin, is added in the printing ink, corrosion or abrasion of the plate or doctor during the printing step cannot be avoided, whereby the amount of the printing ink attached for forming the printed pattern layer may change in the course of printing or the attached portion may become inprecise, thus having the drawback that the unevenness effect obtained becomes unstable and an uneveness effect of good quality cannot be obtained.
Furthermore, the method utilizing the liquid repellent performance possessed by the printed pattern layer of the above 7) has the drawbacks such that the inter-paper strength of the decorative sheet obtained is not sufficient, and that a product having excellent surface characteristics such as abrasion resistance cannot be obtained.
Furthermore, the method utilizing the liquid repellent performance possessed by the printing pattern layer of the above 7) has the drawbacks such that the amount of the coating agent coated during formation of the top coating layer is limited to give a product that does not have excellent surface characteristics such as abrasion resistance.
Also, in any of the methods for producing the decorative plate of the prior art as described above, a top coating layer is formed onto the base paper for a decorative sheet attached with a printed pattern layer, and therefore the amount of the resin utilized for formation of the top coating layer is of itself limited. As a result the sensation of unevenness of the obtained embossing is poor, and a product having excellent quality in physical properties cannot be obtained. Additionally since a decorative sheet having a top coating layer is laminated onto a substrate for decorative plate, there is the drawback such that the a decorative plate has a defect in surface smoothness due to the surface irregularity of the substrate.
In contrast, the process of the present invention is a process for producing a decorative sheet having a corresponding embossed effect which comprises utilizing the liquid repellent performance possessd by the printed pattern layer with a curable type resin, thereby forming a top coating layer with the portion corresponding to said printed pattern layer. Curing of the curable resin as a vehicle in the printing ink is accomplished after applying the printing ink on base paper for a decorative sheet, without the progress of the curing reaction of the curable resin utilized as the vehicle in the printing ink. Also, the curing agent or catalyst is maintained neutral during printing, and therefore there is no corrosion, abrasion, etc. of the plate or doctor to give stable printed pattern layer. Thus, it is intended to provide a process for producing a decorative sheet which can produce a decorative sheet with sharp concavities at the surface of the decorative sheet, and with good efficiency and yet stability, and also a process for producing decorative plates using the decorative sheet.